A horror mass shooting has claimed the lives of four people after a disgruntled NFL video tournament player opened fire on fellow contestants.

Multiple people have been killed at the Madden NFL video game tournament in Jacksonville, Florida at a venue called Good Luck Have Fun inside Chicago Pizza Landing during a live Twitch streaming of the event.

The LA Times reports that a gunman was a disgruntled player who had lost in the $5,000 tournament. He opened fire on others before turning the gun on himself.

In footage streamed online through Twitch nine gunshots can be heard before there are several screams and shouts.

Police barricade a street near the Jacksonville Landing in Jacksonville,

As the shots sound, you can hear repeatedly “oh my god” while 15 people were reportedly shot.

Four people are feared dead with police confirming the suspect was pronounced dead at the scene. A manhunt was launched for a second suspect but police confirmed at 9.30pm GMT that there was only one shooter.

His identity has not been revealed but police say he was a white male.

The coast guard patrols the St John's river outside of the Jacksonville Landing in Jacksonville

"We have no outstanding suspects at this time. No outstanding suspects," Jacksonville Sheriff Mike Williams said at a news conference. "We have one suspect in this case. He is deceased at the scene."

Police confirmed there had been a "mass shooting" at the centre and warned people to stay away from the area - but they are yet to confirm any details about victims. President Trump has been briefed.

Terrified bystanders fled the scene with officers finding them hidden in locked areas of the commercial complex.

SWAT teams are continuing to scour the area.

Footage shows two young men playing in the Madden Championship Series when suddenly shots can be heard in the background.

The stream cuts out, but the audio is still live and people can be heard screaming out in pain in the background.

Memorial Hospital in Jacksonville, Florida is treating at least three patients that were involved in the gaming shooting, according to CNN.

Jacksonville Police wrote on Twitter: "Mass shooting at the Jacksonville Landing. Stay far away from the area. The area is not safe at this time. STAY AWAY."

We can't stress enough to stay away. Many blocks away," they said in a subsequent tweet.

The office added in another tweet: “We are finding many people hiding in locked areas at The Landing. We ask you to stay calm, stay where you are hiding. SWAT is doing a methodical search inside The Landing. We will get to you. Please don’t come running out.”

Local news footage showed several ambulances, as well as firefighters and police officers, on the scene, as well as roads being blocked off in the downtown area.

he Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is responding to the scene in Jacksonville Landing, a law enforcement source told CNN.

Coast Guard boats are patrolling the river.

Spectators watch the Madden tournaments, hoping to pick up skills and tips from more experienced gamers.

Madden NFL is an American football video game series developed by EA Tiburon for EA Sports.

It is named after Pro Football Hall of Famer John Madden, and has sold more than 130 million copies.